BRISTOL — The town was forced yesterday to close off the western end of Woodlawn Avenue after a concrete sewer pipe eroded under Wood Street and created a 10-foot-deep sinkhole.

A motorist Monday night reported to the police the appearance of a small, circular hole in the asphalt on Wood Street at the intersection with Woodlawn Avenue. Upon further inspection, town workers found that a much larger chasm, measuring about eight feet by eight feet, lay underneath the thin layer of asphalt. They immediately blocked off the road at the southern end of town and ordered emergency repairs.

Yesterday, standing above the hole, Town Administrator Diane Mederos said it’s fortunate it was found before an accident occurred. Imagine if a heavy truck or school bus had driven over the hole, she said.

“We’re lucky this was caught when it was,” she said. “This could have been a disaster.”

The hole was created by corrosive gas bubbling up from the sewer pipe, according to Joe Federico, an associate with Beta Engineering. The pipe running south along that stretch of Wood Street toward the town’s water treatment plant is on a downward slope, which causes turbulence in the wastewater running inside. Hydrogen sulfide gas released from the churned water slowly ate away at the reinforced concrete pipe, which dates to the mid-1980s.

“This deteriorated over a long time,” said Matthew A. Calderiso Jr., superintendent of the town’s Water Pollution Control Department.

When the 27-inch pipe gave way, the 10 feet of soil overhead collapsed and washed downstream in the water flow, leaving an empty void underneath the asphalt road. A hole in the asphalt must have opened up some time Monday, Calderiso said. There was no sewage overflow.

The town has hired local contractor C.B. Utility to replace 475 feet of concrete pipe on Wood Street with new plastic pipe. The company has postponed a job in Coventry to carry out the emergency repairs in Bristol.

The work was set to begin last night. Calderiso expects the project to take up to a week. In the meantime, the wastewater that courses through the pipe will be diverted.

Because of the repair work, people who live on Woodlawn must either use Metacom Avenue or Garfield Avenue to reach their homes, Mederos said.

akuffner@projo.com